Telescoping step ladder

ABSTRACT

A ladder assembly for attachment to a side support surface is provided which includes a ladder having an upper and a lower frame portion which automatically telescope in response to an operator from an operative configuration and position wherein the ladder is slightly tilted to a stored configuration and position wherein the ladder is telescoped to a shorter length than in the operative condition and is positioned parallel to the side support surface. A dash-pot type cylinder is included which limits the rate of extension and retraction of the ladder.

United States Patent Wallk TELESCOPING STEP LADDER [75] Inventor: Harold J. Wallk, Mendota, Ill.

[73] Assignee: Caterpillar Tractor Co., Peoria, Ill.

[22] Filed: June 13, 1974 [21] Appl. No.: 479,170

[52] US. Cl 182/96, 182/98, 182/207,

[51] Int. Cl. E06c 5/04 [58] Field of Search 182/97, 98, 96, 95, 207, 182/208, 90; 280/166 [56] References Cited UNITED STATES PATENTS 2,611,466 9/1952 Biggert 280/166 3,012,633 12/1961 Magee 182/96 3,190,392 6/1965 Ashton 182/97 3,379,280 4/1968 Pace 182/96 Mar. 4, 1975 4/1970 Lypko 182/97 8/1971 Saucier 182/96 Primary E.raminerReinaldo P. Machado Attorney, Agent, or FirmPhillips, Moore, Weissenberger, Lempio & Strabala [57] ABSTRACT 7 Claims, 3 Drawing Figures TIELESCOPING STEP LADDER BACKGROUND OF THE INVENTION This invention relates to a ladder assembly for disposition on the side of a structure having a provision for retraction of the ladder assembly from its operative to a stored position and configuration against the side of the structure. More particularly, this invention is directed to a retractable ladder for use on vehicles such as large earth-moving vehicles.

While the following discussion concerns use on earth-moving vehicles, it is to be understood that such is merely for the sake of convenience. The invention has wider application to other uses where similar requirements are present.

As the size and complexity of large earth-moving machines increases, one problem that is encountered is that of providing easy access to various portions thereof including the drivers station and numerous service areas. In the past, use of permanently fixed ladders on vehicles necessarily within easy reach of the ground support surface has not been satisfactory. This is the case since the bottom portions thereof are usually placed below the normal ground clearance of the vehicle and therefore in a position to be damaged when the machine is in motion. In attempts to solve this problem, various types of retractable steps have been devised which can be pivoted or lifted out ofthe way. Examples are shown in U.S. Pat. No. 3,603,429 to Shepherd, and U.S. Pat. No. 3,826,337, to Liptak, the latter being assigned to the assignee hereof. Nevertheless, most of these prior art ladders are still subject to being damaged and in some cases can be shaken or jarred loose during vehicle operation. These ladders also require operator effort to return them back to the stored position, something that is not always done.

To solve this problem, self-retracting ladders such as that shown in U.S. Pat. No. 3,584,704 to Eckmann have been proposed. However, these are limited to a single step and are thus not suitable for applications where substantial height above the ground support surface is involved. Other prior art ladders such as that shown in U.S. Pat. No. 3,012,633 to Magee include a plurality of steps and a pantograph link arrangement with biasing springs to return the ladder to the stored position. This last type of ladder is not entirely satisfactory since it is essentially the same size in its stored as in its operative position.

Summary and Objects of the Invention It is therefore the primary object of this invention to provide a ladder that overcomes the above-noted disadvantages.

It is particularly an object of this invention to provide a ladder which is automatically retractable from its operative position to a stored position responsive to operator utilization.

It is also an object to provide such a ladder which is simple and inexpensive and wherein the rate of extension and retraction is limited.

It is a still further object of this invention to provide such a ladder which takes up less space in its stored than its operative position.

The invention takes the form of a ladder assembly for disposition on the side of a supporting structure comprising an upper and a lower frame with rungs, and

linkage for telescoping the upper with respect to the lower frame. A spring-loaded dash-pot type cylinder limits the rate of extension and retraction of the ladder assembly and automatically returns the ladder assembly to a stored position against the side supporting structure.

Other objects and advantages will become more readily apparent to one having skill in the art to which the invention pertains by having reference to the following description and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a side elevation view ofa wheel loader vehicle showing a ladder mounted thereon in its stored position;

FIG. 2 is an enlarged view of the ladder of FIG. 1 illustrating details thereof; and,

FIG. 3 is a side view of the same and showing the extended, operative position of the ladder in phantom line.

DETAILED DESCRIPTION Referring to FIG. 1 there is shown generally at 10 a wheel loader vehicle having a ladder assembly 12 mounted on the side of the rear frame 14 thereof and shown in its stored condition. The ladder assembly 12 is adapted for allowing an operator to climb between the ground support surface 16 and the operator station shown generally at 18 as will be hereinafter described.

As best seen in FIG. 2, the ladder assembly 12 comprises an upper frame portion 20 and a lower frame portion 22 interconnected by linkage assemblies 24,26. The upper frame portion comprises a pair of vertical, tubular side members 28,30, interconnected by a plurality of spaced apart horizontal rungs 32,34,36. Lower frame portion 22 similarly comprises a pair of tubular side members 38,40 of a diameter so as to slidingly fit within members 28,30. Side members 38,40 are similarly interconnected by a plurality of spaced apart rungs 42,44,46. Upper portions 48,50 of side members 38,40 are of a length to telescope within side members 28,30.

Taking linkage assembly 26 as exemplary, each linkage assembly comprises an upper elongated link member 52, a lower elongated link member 54, and an interconnecting intermediate link member 56 connected thereto by pivots 58,60. As best seen in FIG. 3, upper link member 52 has one end thereof pivotally connected to upper frame portion 20 by pivot 62 and the other end thereof to the frame or side support surface 14 by pivot 64. Similarly, lower link member 54 has one end thereof pivotally connected to lower frame portion 22 by pivot 66 and the other end thereof to frame 14 by pivot 68.

The upper link member 52 is also pivotally connected to one end of a spring biased dash-pot type cylinder 70 by pivot 72. The other end of the cylinder is similarly connected to frame 14 by pivot 74.

In operation, the weight of an operator stepping onto one of the ladder rungs causes the ladder assembly 12 to move from its stored position parallel to frame 14 to its operative position shown at 12'. As may be seen, lower frame portion 22 telescopes out of upper frame portion 20 to an operative position as shown at 22, 20', due to the fact that link member 54 is longer than link member 52. The difference in link length also causes the complete ladder to tilt slightly as shown at 12 to facilitate climbing by the operator. The dash-pot type cylinder limits the rate of extension and retraction of the ladder assembly and is spring loaded by a spring- (not shown). Since the spring is compressed as the ladder assembly is extended, it will automatically return the ladder assembly to the stored position when released by the operator. The telescoping action of the ladder assembly also results in its taking up less space in the stored as opposed to its operative condition.

It is to be understood that other variations are contemplated and that the invention is not to be limited except by the scope of the appended claims.

What is claimed is:

1. In a ladder assembly for attachment to a side support surface including a ladder having an upper frame portion and a lower frame portion, means for telescoping said ladder from an operative length and position to a shorter, stored length and position, and further including means for automatically extending said ladder from its stored length and position to its operative length and position in response to an operator thereon and for causing the ladder to be retracted to its stored length and position when released by the operator.

2. The invention of claim 1 wherein said upper frame portion comprises a pair of elongated side members joined together by a plurality of rung members, and said lower frame portion comprises a pair of elongated side members slidingly fitted with respect to said upper portion side members and joined together by a plurality of rung members.

3. The invention of claim 2 wherein said means for telescoping said ladder comprises a pair of upper, elon gated link members pivotally connected to said upper frame portion, a pair of lower elongated link members pivotally connected to said lower frame portion and an intermediate, elongated link member pivotally connecting a respective upper to a lower link member.

4. The invention of claim 3 wherein said lower link members are longer than said upper link members so that the lower frame portion telescopes with respect to said upper frame portion and the ladder tilts so as to facilitate climbing by the operator.

5. The invention of claim 3 wherein said automatic means comprises a dash-pot cylinder for limiting the rate of extension and retraction of said ladder assembly which includes spring means.

6. The invention of claim 2 wherein said upper frame portion side members are tubular and define a hollow therein.

7. The invention of claim 6 wherein said lower frame portion side members are tubular and of a diameter less than that of said upper frame portion side members so that said lower frame portion side members are slidingly fitted within said upper frame portion side members to telescope therein.

l l= =l 

1. In a ladder assembly for attachment to a side support surface including a ladder having an upper frame portion and a lower frame portion, means for telescoping said ladder from an operative length and position to a shorter, stored length and position, and further including means for automatically extending said ladder from its stored length and position to its operative length and position in response to an operator thereon and for causing the ladder to be retracted to its stored length and position when released by the operator.
 2. The invention of claim 1 wherein said upper frame portion comprises a pair of elongated side members joined together by a plurality of rung members, and said lower frame portion comprises a pair of elongated side members slidingly fitted with respect to said upper portion side members and joined together by a plurality of rung members.
 3. The invention of claim 2 wherein said means for telescoping said ladder comprises a pair of upper, elongated link members pivotally connected to said upper frame portion, a pair of lower elongated link members pivotally connected to said lower frame portion and an intermediate, elongated link member pivotally connecting a respective upper to a lower link member.
 4. The invention of claim 3 wherein said lower link members are longer than said upper link members so that the lower frame portion telescopes with respect to said upper frame portion and the ladder tilts so as to facilitate climbing by the operator.
 5. The invention of claim 3 wherein said automatic means comprises a dash-pot cylinder for limiting the rate of extension and retraction of said ladder assembly which includes spring means.
 6. The invention of claim 2 wherein said upper frame portion side members are tubular and define a hollow therein.
 7. The invention of claim 6 wherein said lower frame portion side members are tubular and of a diameter less than that of said upper frame portion side members so that said lower frame portion side members are slidingly fitted within said upper frame portion side members to telescope therein. 